Preheat oven 350° Cook chicken breasts and cube. Place in the bottom of a buttered, deep casserole dish. Mix sour cream, cream of chicken soup, cream cheese, and poppy seeds (1 tsp). Pour mixture on top of chicken.
Cover with crushed Ritz crackers and drizzle with butter. Sprinkle with remaining poppy seeds. Bake for approx. 40 minutes until bubbly.